Semiconductor device having multiple active area layers and its formation thereof

Abstract

A semiconductor device and method of forming the same are described. A semiconductor device includes an active area adjacent a channel in a semiconductor composite. The active area includes a first active area layer having a first dopant concentration, a second active area layer having a second dopant concentration over the first active area layer, and a third active area layer having a third dopant concentration, over the second active area. The third dopant concentration is greater than the second dopant concentration, and the second dopant concentration is greater than the first dopant concentration. The channel includes a second channel layer comprising carbon over a first channel layer and a third channel layer over the second channel layer. The active area configuration improves drive current and reduces contact resistance, and the channel configuration increases short channel control, as compared to a semiconductor device without the active area and channel configuration.

What is claimed is: 
     
       1. A semiconductor device comprising:
 an active area comprising:
 a first active area layer comprising germanium and having a first dopant concentration, wherein a percentage of the germanium in the first active area layer increases from a bottom surface of the first active area layer to a top surface of the first active area layer; 
 a second active area layer having a second dopant concentration, the second active area layer over the first active area layer; and 
 a third active area layer having a third dopant concentration, the third active area layer over the second active area layer and extending above a top surface of a semiconductor composite within which the first active area layer and the second active area layer are formed, where the first dopant concentration is less than the second dopant concentration, and the second dopant concentration is less than the third dopant concentration. 
 
 
     
     
       2. The semiconductor device of  claim 1 , comprising:
 a channel within the semiconductor composite and adjacent the active area, the channel comprising:
 a first channel layer; 
 a second channel layer over the first channel layer; and 
 a third channel layer over the second channel layer. 
 
 
     
     
       3. The semiconductor device of  claim 2 , the first active area layer having a first active area layer depth, the second channel layer having a second channel layer height and the third channel layer having a third channel layer height, the first active area layer depth greater than a sum of the second channel layer height and the third channel layer height. 
     
     
       4. The semiconductor device of  claim 3 , the sum of the second channel layer height and the third channel layer height less than or equal to about 40nm. 
     
     
       5. The semiconductor device of  claim 2 , wherein:
 the first channel layer is a germanium doped silicon layer, 
 the second channel layer is an epitaxially grown silicon carbide layer, and 
 the third channel layer is an epitaxially grown silicon layer. 
 
     
     
       6. The semiconductor device of  claim 2 , comprising a gate structure over the channel and adjacent the third active area layer. 
     
     
       7. The semiconductor device of  claim 6 , the gate structure spaced apart from the third active area layer by a gap. 
     
     
       8. The semiconductor device of  claim 1 , at least one of:
 the first dopant concentration below 1 e 19 cm −3  of a first p-type dopant; or 
 the first dopant concentration between about 1 e 20 cm −3  to about 3e 20 cm −3  of a first n-type dopant. 
 
     
     
       9. The semiconductor device of  claim 1 , at least one of:
 the second dopant concentration between about 5 e 19 cm −3  to about 5 e 20 cm −3  of a second p-type dopant; or 
 the second dopant concentration between about 2 e 20 cm −3  to about 7 e 20 cm −3  of a second n-type dopant. 
 
     
     
       10. The semiconductor device of  claim 1 , at least one of:
 the third dopant concentration between about 3 e 20 cm −3  to about 5 e 21 cm −3 of a third p-type dopant; or 
 the third dopant concentration between about 3 e 20 cm −3  to about 5 e 21 cm −3 of a third n-type dopant. 
 
     
     
       11. The semiconductor device of  claim 1 , the second active area layer comprising germanium, wherein a percentage of the germanium in the second active area layer increases from a bottom surface of the second active area layer to a top surface of the second active area layer. 
     
     
       12. The semiconductor device of  claim 11 , wherein:
 the first active area layer has a germanium concentration of between about 10% to about 40%, and 
 the second active area layer has a germanium concentration of between about 20% to about 60%. 
 
     
     
       13. A method of forming a semiconductor device comprising:
 forming a channel comprising:
 implanting a first dopant into a substrate and annealing to form a first channel layer in the substrate; 
 growing silicon carbide over the first channel layer to form a second channel layer over the first channel layer; and 
 growing silicon over the second channel layer to form a third channel layer over the second channel layer, a semiconductor composite comprising the first channel layer, the second channel layer and the third channel layer; and 
 
 forming an active area adjacent the channel, comprising:
 forming a first active area layer in the semiconductor composite, the first active area layer having a first dopant concentration; 
 forming a second active area layer in the semiconductor composite, the second active area layer having a second dopant concentration and formed over the first active area layer; and 
 forming a third active area layer over a top surface of the semiconductor composite, the third active area layer having a third dopant concentration and formed over the second active area layer. 
 
 
     
     
       14. The method of  claim 13 , comprising:
 performing a halo implant into the semiconductor composite prior to forming the first active area layer. 
 
     
     
       15. The method of  claim 13 , the forming the first active area layer comprising:
 forming a first opening in the semiconductor composite; and 
 growing at least one of silicon or germanium in the first opening in the presence of at least one of a first n-type dopant or a first p-type dopant, such that the first active area layer comprises at least one of:
 the first dopant concentration below 1 e 19 cm −3  of the first p-type dopant; or 
 the first dopant concentration between about 1 e 20 cm −3  to about 3 e 20 cm −3  of the first n-type dopant. 
 
 
     
     
       16. The method of  claim 13 , the forming the second active area layer comprising:
 growing at least one of silicon or germanium over the first active area layer in the presence of at least one of a second n-type dopant or a second p-type dopant such that the second active area layer comprises at least one of:
 the second dopant concentration between about 5 e 19 cm −3  to about 5 e 20 cm −3  of the second p-type dopant; or 
 the second dopant concentration between about 2 e 20 cm −3  to about 7 e 20 cm −3  of the second n-type dopant. 
 
 
     
     
       17. The method of  claim 13 , the forming the third active area layer comprising:
 growing at least one of silicon or germanium over the second active area layer in the presence of at least one of a third n-type dopant or a third p-type dopant such that the third active area layer comprises at least one of:
 the third dopant concentration between about 3 e 20 cm −3  to about 5 e 21 cm −3  of the third p-type dopant; or 
 the third dopant concentration between about 3 e 20 cm −3  to about 5 e 21 cm −3 of the third n-type dopant. 
 
 
     
     
       18. A semiconductor device comprising:
 an active area, comprising:
 a first active area layer in a semiconductor composite, the first active area layer having a first dopant concentration and a top surface of the first active area layer co-planar with a top surface of the semiconductor composite, and wherein:
 the first active area layer comprises germanium, and 
 a percentage of the germanium in the first active area layer increases from a bottom surface of the first active area layer to a top surface of the first active area layer; 
 
 a second active area layer in the semiconductor composite, the second active area layer having a second dopant concentration and formed over the first active area layer and a top surface of the second active area layer co-planar with the top surface of the semiconductor composite; and 
 a third active area layer over the top surface of the second active area layer, the third active area layer having a third dopant concentration and formed over the second active area layer, where the first dopant concentration is less than the second dopant concentration, and the second dopant concentration is less than the third dopant concentration. 
 
 
     
     
       19. The semiconductor device of  claim 18 , a channel within the semiconductor composite and adjacent the active area, the channel comprising:
 a germanium doped silicon layer, 
 an epitaxially grown silicon carbide layer over the germanium doped silicon layer, and 
 an epitaxially grown silicon layer over the epitaxially grown silicon carbide layer. 
 
     
     
       20. The semiconductor device of  claim 18 , the second active area layer comprising germanium, wherein a percentage of the germanium in the second active area layer increases from a bottom surface of the second active area layer to a top surface of the second active area layer.